2008-2009 PSAS / PSU

ECE Capstone

Team members

Ai Ling Chen, David Loupin, Jeremy Booth, Ken Zeigler, Mike Engstrom, Scott Schuehle

Academic Advisor

Allen TaylorPSAS Advisors

Andrew and Tim

Team Member Responsibilities:

• Ken: GFE, SPS, HAP, Microprocessor• Scott: Power Switches, USB Hub, Umbilical• David: Battery and Charging Systems• Ai Ling: Pressure & Battery Sensors, USB Hub • Firmware: Mike, Jeremy

Avionics Power System (APS)

Generic Front End (GFE) Update

• More Powerful SPS (Switching Power Supply)– More capacity for handling Radios etc

• HAP (Highly Available Power supply)– Optional for all nodes– HAP availability at node configuration

• More capable microcontroller– Additional Interfaces

• Component availability and capability review

GFE Requirements• General

– Parts cost <150$ in small quantities – Board size (,20,25)cm^2 – Board height (,,12)mm

• Interfaces – MUST use a polarized and locking connector – SHOULD be able to be non-locking during development – MUST be rated at (100,500,) mating cycles – MUST have (2,4,) high reliability, high current (2,5,) A rated contacts for

power – Must have (2,4,) high reliability contacts for USB data – Must have (2,4,) high reliability contacts for back-channel bus – Must minimize board area.

GFE Block Diagram

APS Connector

Frontend Passives

Active Protection

SPS (LT3972)

HAP Charger

(LTC4085)

HAP LiPo Battery

HAP Output Regulator

(TPS63000)

USB Interface

CAN Interface JTAG

Connector

Microcontroller(LPC2368)

Node Specific Devices

Switch Network

SPS and HAP Power Path

• Front End Passive Block• Active Protection• SPS (LT3972) Switching DC-DC• HAP Battery Bypass• HAP Output Regulator (TPS63000)

node5-frontend.sch

Switching Power Supply (SPS)

• Front End Passives– EMI Choke, Fuse, Surge Arrestor (semi Zener),

Capacitor• Active Protection Circuits– Circuit Breaker, Overload Detector

• LT3972– 33V, 3.5A, Step-Down Switching Regulator with

75μA Quiescent Current, in sync at 1.5MHz

SPS Requirements– Circuit must be fault tolerant/resistant/robust – High Efficiency (prolong Battery life) – Low Quiescent Current Draw (prolong battery life) – High Frequency Switching (1.5 MHZ) (less audio noise) – Frequency Sync to external source (Makes noise filtering easier) – OVP (survive over-voltages) – UVLO (survive under-voltages) – Vin (10V, 14.8V, 20V) (Voltage supplied by APS node) – Vout1 (3.0,3.3,3.5) V – Vout2 (4.8,5.0,5.2) V – Iout1 max (0.030,1,)A (range may require changes in component values) – Iout2 max (0.030,1,)A (range may require changes in component values) – Low noise – Soft start

Highly Available Power Supply (HAP)

• Charger IC (LTC4085)• Battery (450mAh)• Mosfet Switch and Ideal Diode• Output Regulator (TPS63000)

HAP Requirements

– MUST use single Li Ion Polymer cell – MUST have a seamless transition from externally powered

to battery-powered – MUST meet standard lithium charge/discharge safety

requirements (thermal, voltage, current, time, fuse) – MUST store enough power to run generic node for (1,4,)

hours (Pyro requirement) – MUST be able to be unpopulated on board (for most nodes) – MUST be able to measure battery voltage – MUST be able to have external charge control (from

microcontroller)

Microcontroller (LPC2368)

• Differences from Old to New• Number of Node configurable GPIO available• Busses Available• Memory and Processing Speed

Microcontroller Requirements

– MUST use a LPC2xxx series microcontroller – MUST have USB and back-channel peripherals – MUST have (32,64,) K RAM – MUST use 12 MHz crystal (for USB) and PLL to

highest Freq.

Interfacing• GFE (GPIO and Analog Connections)

– Connections to onboard GFE devices• CAN (Controller Area Network)

– Primarily used for off-board communications• USB (Universal Serial Bus)

– Primarily used for off-board communications• SPI (Serial Peripheral Interface)

– Used for communication to on board devices• I2C (Inter-Integrated Circuit Bus)

– Used for communication to on board devices• 1 Wire (One Wire)

– Used for communication to onboard devices• Analog

– Onboard A/D and D/A pins are available

Hurdles

• Datasheet Contents and Research• Component Tracking during research– Rejected list

• Modeling– Missing LT-Spice models– Models that don’t match reference designs

• Component Packages• Eagle Schematics, Libraries, Layout• GIT and other Open Source Software

Avionics Power System

An Overview

APS Key Functions

• Distribute Battery/Shore power to all other rocket nodes via a network of power switches– Provide a means of control over which nodes

receive power– Provide over current protection to downstream

devices – Distribute data signals to attached devices via

power switch connectors

APS Key Functions

• Umbilical Shore Power connection– Simultaneously charges the APS battery and

provides power to the rocket systems during charging

– Provides an avenue for communication between land based computer and APS system

– Provides a “launch-detect” signal which indicates that launch has occurred

APS Key Functions

• USB Hub– Distributes USB data to downstream devices via

power switch connectors– Configurable for low, full and high speed USB

differential signaling

APS Power Switches

Power Distribution, Protection and Control

Specifications/Requirements• MUST have (8,,) independent resettable electronic circuit breakers

with adjustable current trip and trip delay. Setting can be via resistor strap, EEPROM, etc. Current trip should be latch-off or selectable.

• MUST have Soft on/off feature • MUST have no mechanical switches in main power path. • MUST indicate power switch on/off state (LED for human, and

electrical signal for APS node) • MAY indicate power switch fault state • MUST operate continuously within 20% of the over-current set point • MUST allow set currents in the range (0.1, 5)A • MUST allow over current transients of 100% for minimum 100 ms

without fault to the load

Design Considerations

• Battery Voltage = 14.8V (Design for operation @ 20V)

• Battery Current = 8.5A• Thermal Considerations• Transients

1 of 7 Power Switch Circuits

TPS2490

• Wide operating voltage (+9V to +80) • Under voltage lockout feature • Simpler reference design than LTC1154 (used

on LV2b APS) • MSOP package • Programmable fault timer • Programmable power limit to limit dissipation

in FET

Si4122DY N-Channel FET

• Large Vds Operating Voltage Range: 40V max

• Low Rds_on: 4.5mOhm at Vds = 10V

• Thermal parameters acceptable with respect to power limiting capability of TPS2490

Spec Verification• Has 8 independent resettable electronic circuit breakers with

adjustable current trip and trip delay. Setting via resistor strap. Current trip latch-off.

• Design provides option for Soft-on feature. No soft-off• No mechanical switches in main power path. • Indicates power switch on/off state (LED for human, and Power

Good signal for APS node) • No indication of power switch fault state • Operates continuously within 20% of the over-current set point • Allows set currents in the range (0.1, 5)A • Allows over current transients of 100% for minimum 100 ms

without fault to the load

USB HubUSB Data Distribution

Specifications/Requirements

• SHOULD be USB 2.0 compliant High Speed (480 Mbps)

• MUST handle (8,,) downstream devices (devices may be further hubs)

• SHOULD have hub status LEDs

Design Considerations

• Hub requires 3.3V power supply• Default configuration settings• Interface with micro-controller for changing

configuration settings

SMSC-USB2517

• Requires 3.3V Power Supply• 64-pin QFN package (smaller than 2507 IC)• Large number of configuration options• Compliant with USB 2.0 low, full and high

speed• Control over configuration options provided to

the ARM microprocessor

Default ConfigurationCFG_SEL Pins = ‘000’

• Strap options enabled • Self-power option enabled • LED mode = speed • Individual power switching • Individual over-current sensing

Configuration Strapping Options

• PHY_BOOST[1:0]– Allows signals to upstream devices be boosted to

4%, 8% or 12%. – Default – No Boost (PHY_BOOSY[1:0]=‘00’)

• NON_REM[2:0]– These pins determine which downstream devices

will be considered removable– Default – All devices set as removable

(NON_REM[2:0] = ‘000’

Spec. Verification

• USB 2.0 compliant for Low Speed, Full Speed and High Speed (480 Mbps)

• Handles 7 downstream devices (devices may be further hubs)

• Has hub status LEDs which also indicate speed of attached devices

Umbilical ConnectionConnecting the Rocket to the Ground

Computer

Specifications/Requirements

• MUST seamlessly shift between shore power and battery power

• MUST be able to detect the presence of shore power

• MUST wake up APS microcontroller if shore power turned on

• MUST be able to sense if connector is inserted or removed (launch detect)

Design Considerations

• Connector type

• Ideal Diode (No longer used)

• Launch detect implementation

Umbilical Connection/Ideal Diode

Spec. Verification

• Ideal Diode allows seamless shift between shore power and battery power

• MUST be able to detect the presence of shore power

• MUST wake up APS microcontroller if shore power turned on

• MUST be able to sense if connector is inserted or removed (launch detect)

Summary

• APS Power Switch Network • USB Hub • Umbilical Connection to APS (Not

Implemented)

Battery and Charging Systems

BatteryBattery requirements• SHOULD be a 4-series cell Li battery• Battery SHOULD cost <500$• Overall Battery SHOULD have energy-mass density (100,,) W.hr/kg• Overall Battery energy-volume density SHOULD be (200,,) W.hr/l• Battery capacity SHOULD be (4,8,) AHr (TODO: TBD on new power budget)• SHOULD have dimensions less than (,3.0,3.5) inches in the cross sectional

plane of the airframe, length (,,10)inches• MUST have a fuse in the pack before the lead• Total battery "unplugged" leakage MUST be < C/(1,5,) year rate (e.g. ~ 100

uA for 4 AHr)

ChargerRequirements: • MUST meet standard lithium charge/discharge safety

requirements (thermal, voltage, current, time, fuse)• MUST be able to charge at (,1C,C/2) rates at internal

air temperature of 50 deg C.* • MAY equalize cells up to some small bypass power

(e.g., .5W)• MUST indicate charging status (on/off)• MAY indicate some kind of charge % (blink rate, color,

LED bar graph, etc)

Internal Charger

Apscharger2.sch

External charger

APSEXTERNALCHARGER.sch

Issues

• Labeling of design sections

• Changes in design

Main tasks:

•Analog pressure sensor

•7-port USB hub controller

•Battery sensor

Analog pressure sensor

Reason to redesign:• The pressure sensor that is currently used is

SCP1000. Its measuring range is from 30 kPa to 120 kPa.

• We want to find a pressure sensor that can accurately measure the pressure from 1 atm down to 0 atm.

Analog pressure sensor

Requirements: MUST have pressure range of 0 - 1 ATM (0 kPa - ~115 kPa, 0 -

~15 PSI) or more Absolute pressure (needs onboard reference) SHOULD use (,3.3,5) V power supply SHOULD use (,10,50) mA current SHOULD have single ended analog output OR digital output MAY have quick response time < 1 ms (~ KHz of bandwidth) MUST have a small package size (0,1,10) cm3

Analog pressure sensor

ASDX DO series: Pressure range from 0 psi to 15 psi (1 psi = 6.9 kPa) Available in absolute, differential and gage types. A single 5.0 Vdc supply The output of the device is a corrected pressure

value in hex format with 12-bit resolution. Therefore, the smallest change in the output given any change in pressure is 5V/(2^12) = 1.22 mV

Response time of 8ms.

Analog pressure sensor

Pressure Sensor Test• Goal: To test pressure sensors to near vacuum

and outside their usual acceleration and temperature ranges. Those sensors are:

• Honeywell ASDX015A24R • Freescale MP3H6115A• VTI SCP1000

Giant vacuum chamber in Dr. Erik Sanchez's lab at PSU in Science Building

Reference: http://psas.pdx.edu/avionics/pressure_sensor_testing/

Analog pressure sensor

Result:• The SCP sensor was accurately reflecting the

pressure recorded on the pressure gauge, even down to 0.45 kPa.

• ASDX worked down to 0.45 kPa as expected. • The MP3 bottomed out due to hitting the

ground rail at ~ 10 kPa

USB Hub controller

Requirements:• One up stream, seven down streams• Small• Powered• High speed• Available

USB Hub controller

USB2507– Integrated USB 2.0 compatible 7-port Hub

• 7-Port Hub• Complete USB Specification 2.0 Compatibility• 1.8 Volt Low Power Core Operation• 3.3 Volt I/O with 5V Input Tolerance.• Available in Digi-Key, $8.75 each

Battery Sensor

Reason to redesign:The old battery sensor didn’t work properly.

Requirements:• MUST monitor charge ("coulomb counter")• MUST measure pack voltage• SHOULD: monitor the voltage on each cell• MUST monitor battery pack temperature (MUST be

compatible with charging chip)• SHOULD separate high current connector from sensing

connector

Battery Sensor

Chosen IC chips:1. DS2788 --- The only chip that works with 1-10 cell Li-ion

Battery.

Features:• Measures voltage, temperature, and current• Estimates available capacity for rechargeable lithium-ion

(Li+) and Li+ polymer batteries. Capacity estimation is reported in mAh remaining and percentage of full.

• LED display drivers and a debounced input make display of the capacity information easy.

• 1-Wire interface• 14-Pin TSSOP Package

Battery Sensor

Chosen IC chips:2. ISL9208 --- Multi-Cell Li-ion Battery Pack OCP/Analog Front

End

Features:• Supports battery pack configurations consisting of 4-cells to 7-

cells in series and 1 or more cells in parallel. • Provides internal cell balancing switches, cell voltage monitor

level shifters, and drive circuitry for external FET devices for control of pack charge and discharge.

• Provides monitoring of each cell voltage plus internal and external temperature by a separate microcontroller with an A/D converter.

• I2C interface• 32 Ld 5x5 QFN Package

Battery Sensor

Schematic (Part 1):

Battery Sensor

Schematic (Part 2):

Battery SensorDraft Layout:

Firmware

Objectives

• Create firmware to run the APS and all its peripherals.

• Real time data collection and response

• Design for graceful/safe failure modes

• Maintain modularity to allow for code re-use in other nodes where possible

Objectives

• Power switching to various subsystems

• Battery Management

• Umbilical disconnect detection

• Error Handling and Logging

• Serial console / UART based control interface

• The nodes were to be standardized on the LPC2368 (ARM7TDMI-S) microcontroller

• They were to run FreeRTOS for multitasking / task management support

• Communication with peripherals and other nodes was to use the following interfaces:CAN USB UART 1-WireSPI I2C Analog GPIO

Objectives

Layout

• Application divided into many tasks

• Tasks grouped by function or interface

• Tasks can act as “gatekeepers” to interfaces, or prioritize resource consumption

LayoutData and

LibrariesOS and

Application

Overcoming Hurdles

• Configuration of Linux system

• Setting up a cross-compiler

• Getting compiled code on the OLIMEX boards

• Tools for collaboration - Git

• Uncertainty and error messages – help!

• Scope of project– Far broader than it initially appeared

• Unfamiliarity with development environment– Linux– Git

• Issues programming via JTAG – Board in “hung” state– Burning JTAG ports

Overcoming Hurdles

The Switch to LPC 2378

• New processor - New version of FreeRTOS• More functionality• Significantly different physical pin setup• Code changes needed– Register initialization– New built in devices/additional ports– Significantly changed FreeRTOS API

Overcoming Hurdles

Accomplishments

• GPIO handling– Simple commands to enable, read and write

• Multi-Channel ADC– All ports and channels available– Simple commands to enable, read and write

LPC2148

Accomplishments

• SPI– Interface suite created– Device specific drivers created

• UART control framework– Acts on commands via UART– Tested to respond to correct input only

LPC2148

Accomplishments

• Error Handling/Logging – Stores sequential list of errors– Reports list of errors and statistics– Uses UART control framework

• I2C (functional outline / algorithms)– Behavior defined for operation of Master states

LPC2148

Accomplishments

• Vibration and Vacuum Chamber tests

• Development board - LPC 2148

• SCP1000 pressure sensor (High Speed SPI)

• ASDX pressure sensor (analog)

• Additional analog sensors

Sensor Testing

Accomplishments

• GPIO Handling– Additional Ports and Pins!– Ports and Pins available per processor type

• Multi-Channel ADC– Single port (fewer total channels!)

LPC2368/78

Accomplishments

• UART control framework– Acts on commands via UART

• FSM (APS specific)– Sleep, Wake, Safe, Armed– Critical inputs determine whether to change state – State sub-functions will perform internal tasks

LPC2368/78